This is a note to let you know that I've just added the patch titled
jfs: jfs_dmap: Validate db_l2nbperpage while mounting
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
jfs-jfs_dmap-validate-db_l2nbperpage-while-mounting.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 11509910c599cbd04585ec35a6d5e1a0053d84c1 Mon Sep 17 00:00:00 2001
From: Siddh Raman Pant <code@xxxxxxxx>
Date: Tue, 20 Jun 2023 22:17:00 +0530
Subject: jfs: jfs_dmap: Validate db_l2nbperpage while mounting
From: Siddh Raman Pant <code@xxxxxxxx>
commit 11509910c599cbd04585ec35a6d5e1a0053d84c1 upstream.
In jfs_dmap.c at line 381, BLKTODMAP is used to get a logical block
number inside dbFree(). db_l2nbperpage, which is the log2 number of
blocks per page, is passed as an argument to BLKTODMAP which uses it
for shifting.
Syzbot reported a shift out-of-bounds crash because db_l2nbperpage is
too big. This happens because the large value is set without any
validation in dbMount() at line 181.
Thus, make sure that db_l2nbperpage is correct while mounting.
Max number of blocks per page = Page size / Min block size
=> log2(Max num_block per page) = log2(Page size / Min block size)
= log2(Page size) - log2(Min block size)
=> Max db_l2nbperpage = L2PSIZE - L2MINBLOCKSIZE
Reported-and-tested-by: syzbot+d2cd27dcf8e04b232eb2@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?id=2a70a453331db32ed491f5cbb07e81bf2d225715
Cc: stable@xxxxxxxxxxxxxxx
Suggested-by: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx>
Signed-off-by: Siddh Raman Pant <code@xxxxxxxx>
Signed-off-by: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/jfs/jfs_dmap.c | 6 ++++++
fs/jfs/jfs_filsys.h | 2 ++
2 files changed, 8 insertions(+)
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -191,7 +191,13 @@ int dbMount(struct inode *ipbmap)
dbmp_le = (struct dbmap_disk *) mp->data;
bmp->db_mapsize = le64_to_cpu(dbmp_le->dn_mapsize);
bmp->db_nfree = le64_to_cpu(dbmp_le->dn_nfree);
+
bmp->db_l2nbperpage = le32_to_cpu(dbmp_le->dn_l2nbperpage);
+ if (bmp->db_l2nbperpage > L2PSIZE - L2MINBLOCKSIZE) {
+ err = -EINVAL;
+ goto err_release_metapage;
+ }
+
bmp->db_numag = le32_to_cpu(dbmp_le->dn_numag);
if (!bmp->db_numag) {
err = -EINVAL;
--- a/fs/jfs/jfs_filsys.h
+++ b/fs/jfs/jfs_filsys.h
@@ -135,7 +135,9 @@
#define NUM_INODE_PER_IAG INOSPERIAG
#define MINBLOCKSIZE 512
+#define L2MINBLOCKSIZE 9
#define MAXBLOCKSIZE 4096
+#define L2MAXBLOCKSIZE 12
#define MAXFILESIZE ((s64)1 << 52)
#define JFS_LINK_MAX 0xffffffff
Patches currently in stable-queue which might be from code@xxxxxxxx are
queue-4.19/jfs-jfs_dmap-validate-db_l2nbperpage-while-mounting.patch
